Sunday, February 17, 2013

In order to study cancer cachexia, we need to use a type of cancer that will cause cachexia in a controlled way. We need to know exactly how long it will take, how the cancer will act, and be confident that it will always produce the same result. There are different lines of cells that will cause cachexia, each with its own benefits and drawbacks. Our lab uses the well-characterised Murine Adenocarcinoma 16 (MAC16) model of cachexia.

They may not look much, but these are lean,
mean, cachexia-causing machines

What do the MAC cells do?

The MAC16 cell line produces a round, isolated tumour at the site of injection. The rate of growth varies a small amount from animal to animal, but it will usually appear as a small bump, like a grain of sand under the skin, at 3-7 days. The MAC16 model is not invasive, in that it does not migrate or infiltrate other organs and cavities, but remains wrapped in its own thin-membraned compartment.

Weight-loss begins around the same time as the tumour appears, gradually at first. Weight-loss is usually significant from around the 12 day mark, and may reach up to 15% of initial body-weight by the end of the study. The weight-loss is caused by a number of different factors, including a number of particular chemicals, or “tumour factors”, secreted by the cancer.

Unlike many other cancer types used in the lab, this cell line does not, in our experienced, decrease appetite. This is very important, because it allows us to make sure that the weight loss is being caused by the cachexia, rather than starvation.

How does your cell-line grow?

Cells can be very temperamental when they are growing outside of an organism. We grow them in plastic flasks, in a liquid nutrient mixture, containing proteins and sugars to nourish them, buffers to keep them at the right pH level, and antibiotics to fight off bacteria. The cells take up the nutrients in this “growth media”, and excrete their waste into it. This means it needs to be changed every 48 hours, so that they aren’t poisoned by their own waste.
The cells are kept at a constant 37C, with 5% Carbon Dioxide, which is roughly the same conditions as they would experience if they were living in a mammal. It takes anywhere between 3 days and 2 weeks for the cells to reach “80% confluence”, which means they have multiplied to the point that cells are taking up 80% of the media volume.

Once they reach 80%, we can do one of three things: split them into new flasks, so they keep growing without smothering themselves, freeze them down to place them in storage, or study what they do in an animal model, which is what we will talk about next.

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A student, a scholar, a sucker for punishment. Lives for the dream, and dreams of the life. A daughter, a demon, a victim to vision, an inamorata, a friend. Horrified by the depth of human ignorance and cruelty, but working toward a less horrific future.